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The sum of the infinite series cot^-1 2+...

The sum of the infinite series `cot^-1 2+cot^-1 8+cot^-1 18+cot^-1 32+........` is equal to

A

`pi`

B

`pi/2`

C

`pi/4`

D

none of these

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The correct Answer is:
C
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PATHFINDER-TRIGONOMETRIC EQUATION AND INVERSE-QUESTION BANK
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